By using the so called HTTP-EQUIV tag you are able to add certain values to your website. HTTP-EQUIV meta tags define the header of an HTML document. This is a section of code that is sent to your browser before the rest of the page. It communicates to your browser certain introductory information about the page. You can think of it as a “Hello, I am a HTML page. I was born on such-and-such a date and live on such-and-such a server. I was last modified on such-and-such a day, etc…
This introductory information is normally never seen by the end user.
Several variaties are possible:
<meta http-equiv="expires" content="date">
Example meta tag <meta http-equiv=”expires”
Add the following meta tag in the HTML source of your page:
<meta http-equiv="expires" content="mon, 27 sep 2015 14:30:00 GMT">
The date has to be added in the RFC850 format.
Example metatag <meta http-equiv=”pragma”
Another variant is:
<meta http-equiv="pragma" content="no-cache">
This tag make sure your page will not remain in the cache of the computer of your visitor. It’s useful if the content of the page regularly changes, e.g. if you have a newspage on your website.
Example meta tag <meta http-equiv=”window-target”
Another variant is the so called window target:
<meta http-equiv="window-target" content="_top">
This meta tag makes sure that others are not able to show your page in a frame on their own website.
Example meta tag <meta http-equiv=”Set-Cookie”
Another variant is the so called set cookie:
<meta http-equiv="Set-Cookie" content="ACCOUNT=9983373;
path=/; expires=Thursday, 20-May-07 00:15:00 GMT">
With this cookie-tag you are able to place cookies that are only temporary or have an expiration date.
( CONTENT=”name=data; path=path; expires=Day, DD-MMM-YY HH:MM:SS ZON”>)
Example meta tag <meta http-equiv=”pics-label”
Another variant is the so called picture label:
<meta http-equiv="pics-label" content="text">
This is a specific tag that provides you the possibility to add a value to the pictures on your website, e.g. “violence”, “erotic” or “for all ages”.
PICS = Platform for Internet Content Selection
Click here for more information about this standard
Example meta tag <meta http-equiv=”refresh”
Another variant is the so called refresh value:
<meta http-equiv="refresh" content="value">
This refresh-tag will automatically redirects you to another webpage.
<meta http-equiv="refresh" content="30; ,URL=http://www.metatags.info/pages/register.php">
The number “30” is the number of seconds and pages/register.php is the page your customer will be redirected to.
Where do you add this http-equiv= tag?
You may add this http-equiv= tag to all of your webpages, so not only in the first index page. Make sure that on every page relevant meta tags are added. Add keywords and phrases that are relevant and correspond to the text and the language on that specific page. It might be a lot of work to add specific meta tags to each page but you will notice in time that it works!
Using HTML To Prevent page from cached:
<meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate" />
<meta http-equiv="Pragma" content="no-cache" />
<meta http-equiv="Expires" content="0" />
Cache-Control is per the HTTP 1.1 spec for clients (and implicitly required by some browsers next to
Pragma is per the HTTP 1.0 spec for clients and proxies and
Expires is per the HTTP 1.1 spec for clients and proxies. Other
Cache-Control parameters are irrelevant if the abovementioned three are specified. The
Last-Modified header as included in most other answers here is only intersting if you actually want to cache the request, so you don’t need to specify it at all.
Note that when the page is served over HTTP and a header is present in both the HTTP response headers and the HTML meta tags, then the one specified in the response header will get precedence over the HTML meta tag. The HTML meta tag will only be used when the page is viewed from local disk file system. See also W3 HTML spec chapter 5.2.2. Take care with this when you don’t specify them programmatically, because the webserver can namely include some default values. To verify the one and other, you can see/debug them using Firebug Net panel.
Here is another detail Useful HTML Meta Tags